Question

Turgeon: Immunology & Serology in Laboratory Medicine, 4th Edition

Case Study: Phagocytosis

History and Physical Examination

M.P. is a 2-year-old girl who came to the United States from India with her parents when she was a baby. Recently, her appetite has been poor, and she has been losing weight. Her mother has noticed that she is not as active as usual.

Physical examination revealed that the girl was underweight for her age. She had a slight cough, and her physician heard wheezes in her left lung.

A chest radiograph, Gram stain, and sputum culture were ordered. The chest radiograph revealed an abnormality of the upper lobe of the left lung.

Laboratory Data

Sputum smear: positive for Mycobacterium tuberculosis

Questions

1. What types of cells of the immune system are active in an M. tuberculosis infection?

a. Neutrophils

b. Lymphocytes

c. Monocytes

d. Alveolar macrophages

2. Why does M. tuberculosis survive phagocytic destruction?

a. Overcomes the action of oxygen and nitrogen radicals

b. Overcomes the action of lysosomal enzymes

c. Inhibits lysosomal fusion

d. All of above

3. Cytotoxic T lymphocytes trigger _____________ in the pulmonary lesion of bacteria.

a. necrosis

b. bacterial multiplication

c. phagocytosis by alveolar macrophages

d. destruction

Answer 1

Ans) 1) d. Alveolar macrophages

Explaination:

- The main role of the inflammasome is to prepare certain immunity proteins in the macrophages, which are called "interleukins." When M. tuberculosis infects the lungs, interleukins from the macrophages are in the first line of defense.

2) d. All of the above

Explaination:

Granulomas consist of immune cells known as macrophages, which engulf the M. tuberculosis bacteria and isolate them in a cellular compartment where the bacteria either cannot grow or are killed. This does not kill the bacteria, and they rapidly grow inside the dead macrophage.

3) c. Phagocytosis by alveolar macrophages

Explaination:

Macrophages are specialised cells involved in the detection, phagocytosis and destruction of bacteria and other harmful organisms. In addition, they can also present antigens to T cells and initiate inflammation by releasing molecules (known as cytokines) that activate other cells.